Highly plasticized poly(vinyl chloride) composites are used in numerous unsupported film applications and coated fabrics. Most commonly used plasticizers volatilize with time resulting in embrittlement and cracking of poly(vinyl chloride) composites. Condensation of the plasticizer also causes fogging of automobile windshields.
Polymers that can be blended with poly(vinyl chloride), PVC, to form flexible products are, therefore, desired. Miscible polymer blends are considered to be exceptionally rare because of unfavorable thermodynamics of polymer mixing. Nevertheless, there are a few examples of polymers that are known to form miscible blends with poly(vinyl chloride). Unfortunately many of these polymers are either difficult to blend with PVC, crystallize on standing to harden the PVC blend or can only be added to the PVC in limited amounts. ("Polymer Blends," Vol. 2 Paul and Newman, Academic Press, Inc., New York, 1978, article by C. F. Hammer, pages 219-242.)
Grafting is one way of improving compatibility between two immiscible polymers. Preparation of graft copolymers of poly(vinyl chloride) using free-radical polymerization techniques is inefficient in that only low amounts of the grafting monomers become chemically attached as grafted polymer to the poly(vinyl chloride) backbone. Compositions resulting from these grafting reactions contain large amounts of ungrafted polymers which are usually incompatible with poly(vinyl chloride). Consequently, the materials have poor physical, optical and processing properties.
Copending U.S. patent application Ser. No. 414,090 filed Sept. 1, 1982 now U.S. Pat. No. 4,423,193 granted Dec. 27, 1983, a continuation of U.S. patent application Ser. No. 287,462 filed July 27, 1981, abandoned, describes a technique for obtaining much higher grafting efficiencies and compatible compositions by grafting acrylic and other unsaturated copolymerizable monomers to partially dehydrochlorinated poly(vinyl chloride) which contains graft sites (polyene sequences). However, in the present invention it is not necessary to use partially dehydrochlorinated poly(vinyl chloride) to prepare the desired flexible compositions.